The present invention relates to materials suitable for use as contact materials for low energy slip rings, and more particularly, to gold based contact materials having elongated zones of a second phase therein.
Materials suitable for use in low energy slip rings should exhibit high wear resistance and low contact resistance. Accordingly, such materials must have high conductivity, high hardness and wear resistance, high tarnish resistance, low contact noise, and little or no tendency towards catalytic formation of friction polymers. In the past, such considerations have led to a virtually exclusive dependence upon gold based materials. Currently used gold-based materials utilize cold working, solid solution hardening, precipitation hardening, or order hardening which generally benefit strength, hardness and wear resistance but have detrimental effects on the electrical and chemical properties of gold.
Nickel, cobalt, or cadmium hardened electroplated gold exhibit high hardness, high wear resistance and have a reasonably high conductivity, but such materials often have included contaminants such as, KCN, porosity, codeposited polymers, and the like. Additionally, properties of hardened electroplated gold are strongly dependent upon the substrate and plating conditions. Thus, consistently high quality electroplates require not easily achieved stringent controls during processing.
With regard to bulk alloys of gold, the choice is limited because many alloying metals which benefit strength or wear resistance severely degrade the electrical and chemical properties of gold. Prior Art approaches include dispersion-hardened gold with insoluble additives such as oxides, carbides, or refractory metals such as Mo, or order hardened gold such as Au.sub.3 Pt.
Accordingly, it is desirable to provide gold based alloy material which will exhibit high hardness, high wear resistance, and high strength, combined with high conductivity.